<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Document</title>
  <link rel="stylesheet" href="https://cdn.bootcss.com/twitter-bootstrap/4.3.1/css/bootstrap.css">
</head>
<body>
  <nav class="navbar navbar-expand-sm navbar-dark bg-primary">
      <a class="navbar-brand" href="#">Navbar</a>
      <button class="navbar-toggler d-lg-none" type="button" data-toggle="collapse" data-target="#collapsibleNavId" aria-controls="collapsibleNavId"
          aria-expanded="false" aria-label="Toggle navigation"></button>
      <div class="collapse navbar-collapse" id="collapsibleNavId">
          <ul class="navbar-nav mr-auto mt-2 mt-lg-0">
              <li class="nav-item active">
                  <a class="nav-link" href="#">Home <span class="sr-only">(current)</span></a>
              </li>
              <li class="nav-item">
                  <a class="nav-link" href="#">Link</a>
              </li>
              <li class="nav-item dropdown">
                  <a class="nav-link dropdown-toggle" href="#" id="dropdownId" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">Dropdown</a>
                  <div class="dropdown-menu" aria-labelledby="dropdownId">
                      <a class="dropdown-item" href="#">Action 1</a>
                      <a class="dropdown-item" href="#">Action 2</a>
                  </div>
              </li>
          </ul>
          <form class="form-inline my-2 my-lg-0">
              <input class="form-control mr-sm-2" type="text" placeholder="Search">
              <button class="btn btn-outline-success my-2 my-sm-0" type="submit">Search</button>
          </form>
      </div>
    </nav>
</body>
</html>